Nutritional Research Series

[Pages:36]Technical Review 17

Nutritional Research Series

Volume 1: Application of Systematic Review Methodology to the Field of Nutrition

Prepared for: Agency for Healthcare Research and Quality U.S. Department of Health and Human Services 540 Gaither Road Rockville, MD 20850 Contract No. 290-02-0022 Prepared by:

Tufts Evidence-based Practice Center, Boston, MA

Investigators Alice H. Lichtenstein, D.Sc. Elizabeth A. Yetley, Ph.D. Joseph Lau, M.D.

AHRQ Publication No. 09-0025 January 2009

This report is based on research conducted by the Tufts Evidence-based Practice Center (EPC) under contract to the Agency for Healthcare Research and Quality (AHRQ), Rockville, MD (Contract No. 290-02-0022). The findings and conclusions in this document are those of the author(s), who are responsible for its content, and do not necessarily represent the views of AHRQ. No statement in this report should be construed as an official position of AHRQ or of the U.S. Department of Health and Human Services.

The information in this report is intended to help clinicians, employers, policymakers, and others make informed decisions about the provision of health care services. This report is intended as a reference and not as a substitute for clinical judgment.

This report may be used, in whole or in part, as the basis for the development of clinical practice guidelines and other quality enhancement tools, or as a basis for reimbursement and coverage policies. AHRQ or U.S. Department of Health and Human Services endorsement of such derivative products may not be stated or implied.

This document is in the public domain and may be used and reprinted without permission except those copyrighted materials noted for which further reproduction is prohibited without the specific permission of copyright holders. Suggested Citation: Lichtenstein AH, Yetley EA, Lau J. Application of Systematic Review Methodology to the Field of Nutrition. (Prepared by the Tufts Evidence-based Practice Center under Contract No. 290-02 0022). AHRQ Publication No. 09-0025. Rockville, MD: Agency for Healthcare Research and Quality. January 2009. No investigators have any affiliations or financial involvement (e.g., employment, consultancies, honoraria, stock options, expert testimony, grants or patents received or pending, or royalties) that conflict with material presented in this report.

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Preface

The Agency for Healthcare Research and Quality (AHRQ), through its Evidence-based Practice Centers (EPCs), sponsors the development of evidence reports and technology assessments to assist public- and private-sector organizations in their efforts to improve the quality of health care in the United States. The reports and assessments provide organizations with comprehensive, science-based information on common, costly medical conditions and new health care technologies. The EPCs systematically review the relevant scientific literature on topics assigned to them by AHRQ and conduct additional analyses when appropriate prior to developing their reports and assessments.

To bring the broadest range of experts into the development of evidence reports and health technology assessments, AHRQ encourages the EPCs to form partnerships and enter into collaborations with other medical and research organizations. The EPCs work with these partner organizations to ensure that the evidence reports and technology assessments they produce will become building blocks for health care quality improvement projects throughout the Nation. The reports undergo peer review prior to their release.

AHRQ expects that the EPC evidence reports and technology assessments will inform individual health plans, providers, and purchasers as well as the health care system as a whole by providing important information to help improve health care quality.

We welcome comments on this evidence report. They may be sent by mail to the Task Order Officer named below at: Agency for Healthcare Research and Quality, 540 Gaither Road, Rockville, MD 20850, or by e-mail to epc@.

Carolyn M. Clancy, M.D. Director Agency for Healthcare Research and Quality

Jean Slutsky, P.A., M.S.P.H. Director, Center for Outcomes and Evidence Agency for Healthcare Research and Quality

Beth A. Collins Sharp, R.N., Ph.D. Director, EPC Program Agency for Healthcare Research and Quality

Stephanie Chang, M.D., M.P.H. EPC Program Task Order Officer Agency for Healthcare Research and Quality

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Nutritional Systematic Reviews

The medical and clinical communities have effectively used systematic reviews to develop clinical and public health practice guidelines, set research agendas, and develop scientific consensus statements. However, the use of systematic reviews in nutrition applications is more recent and limited. The Office of Dietary Supplements (ODS) at the National Institutes of Health (NIH) has been proactive and developed an evidence-based review program using the EPC Program established by AHRQ, as part of a Congressional mandate to review the current scientific evidence on the efficacy and safety of dietary supplements and identify research needs (). To date, this program has sponsored 17 evidence reports on a range of supplement-related topics including B-vitamins, ephedra, multivitamin/mineral supplements, omega-3 fatty acids, soy, and vitamin D. ODS is currently sponsoring an augmentation of the vitamin D report published in August 2007 to provide relevant information for a pending Institute of Medicine review of the current Dietary Reference Intakes for vitamin D and calcium. The completed ODS-sponsored evidence reports have resulted in numerous associated publications in scientific journals, have formed the basis for an NIH-sponsored state-of-the-science conference, and have been used to assist in setting research agendas.

To facilitate a better understanding of the challenges involved in conducting nutrition-related systematic reviews and in integrating these reviews with nutrition applications for which such reviews have not been previously used, ODS has sponsored the development of a series of technical reports via the EPC Program. The purpose of these reports was to: a) identify the challenges, advantages, and limitations of conducting nutrition-based systematic reviews; b) work with a panel of experts to explore approaches for integrating systematic reviews into processes associated with the derivation of nutrient intake reference values; c) identify the breadth and quality of currently available nutrition-related systematic reviews against generally accepted quality guidelines within the context of the unique needs for nutrition topics; and d) critically explore the consistencies and inconsistencies in results between observational and intervention studies and evaluate how the formulation of research questions may have contributed to these discrepancies.

Paul M. Coates, Ph.D. Director, Office of Dietary Supplements National Institutes of Health

Elizabeth A. Yetley, Ph.D. Senior Nutrition Research Scientist Office of Dietary Supplements National Institutes of Health

National Institutes of Health

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Structured Abstract

Systematic reviews represent a rigorous and transparent approach of synthesizing scientific evidence that minimizes bias. They evolved within the medical community to support development of clinical and public health practice guidelines, set research agendas and formulate scientific consensus statements. The use of systematic reviews for nutrition related topics is more recent. Systematic reviews provide independently-conducted comprehensive and objective assessments of available information addressing precise questions. This approach to summarizing available data is a useful tool for identifying the state of science including knowledge gaps and associated research needs, supporting development of science-based recommendations and guidelines, and serving as the foundation for updates as new data emerge.

Our objective is to describe the steps for performing systematic reviews and highlight areas unique to the discipline of nutrition important to consider in data assessment. Steps involved in generating systematic reviews include identifying staffing and planning for outside expert input, forming a research team, developing an analytic framework, developing and refining research questions, defining eligibility criteria, identifying search terms, screening abstracts according to eligibility criteria, retrieving articles for evaluation, constructing evidence and summary tables, assessing methodological quality and applicability, and synthesizing results including performing meta-analysis, if appropriate.

Unique and at times challenging, nutrition related considerations include baseline nutrient exposure, nutrient status, bioequivalence of bioactive compounds, bioavailability, multiple and interrelated biological functions, undefined nature of some interventions, and uncertainties in intake assessment. Systematic reviews are a valuable and independent component to decision making processes by groups responsible for developing science-based recommendations and policies.

Key words: Systematic review, evidence-based, diet, nutrition recommendations, nutrition guidelines.

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Contents

Evidence Report ....................................................................................................................... 1

Chapter 1. Introduction ............................................................................................................ 3

Examples of recent systematic reviews of nutrition related topics......................... 3

Chapter 2. Systematic Review Methodology............................................................................ 5

Identify staffing....................................................................................................... 5

Form multidisciplinary research team ................................................................... 5

Plan for outside inputs ........................................................................................... 6

Develop analytic framework .................................................................................. 6

Develop and refine research questions .................................................................. 6

Define eligibility criteria ........................................................................................ 7

Identify search terms .............................................................................................. 7

Perform literature search ........................................................................................ 8

Evaluate search results ........................................................................................... 8

Construct evidence and summary tables, and extract data .................................... 8

Assess methodological quality and applicability of studies .................................. 9

Perform meta-analysis, as appropriate ................................................................... 9

Synthesize results ................................................................................................... 10

Chapter 3. Discussion .............................................................................................................. 11

Unique Considerations When Conducting Nutrition-Related Systematic

Reviews.................................................................................................................... 11

Baseline Exposure ................................................................................................... 11

Nutrient Status ........................................................................................................ 11

Bioequivalence of Different Chemical Forms of Nutrients .................................... 11

Bioavailability of Nutrients ..................................................................................... 12

Multiple and Interrelated Biological Functions of a Nutrient ................................. 12

Undefined Nature of Nutrient Intervention ............................................................. 12

Uncertainties in Assessing Dose Response Relationships ...................................... 13

Strengths and Limitations of Systematic Review Approach for Nutrition

Applications........................................................................................................ 13

Chapter 4. Conclusion............................................................................................................... 15

References................................................................................................................................. 17

List of Acronyms/Abbreviations............................................................................................... 21

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